WebSep 26, 2024 · Focal length, f = = = 25 cm It will provide a convex mirror. Question 28. Which property of concave mirror is utilised for using them as shaving mirrors? Answer: When an object is placed between the pole and focus of concave mirror a magnified, erect and virtual image is obtained. Question 29. What is an optically rarer medium? Answer: WebIn fact, it is usually referred to as lens power. Normally, the focal length of a lens uses millimeter as a unit such as 50mm, 100mm, 8.9mm and 71.mm. The lens power …
Focal length - Wikipedia
WebApr 11, 2024 · The power of a lens is measured as the reciprocal of the focal length of the lens. Relation with focal length: A lens of less focal length produces more converging or diverging and is said to have more power. I.e., P = 1/ F According to the lens maker’s formula, 1/ F = (v - 1) ( 1 R 1 − 1 R 2 ) Since, P = 1/ F We get, P = (v - 1) ( 1 R 1 − 1 R 2 ) WebA larger objective focal length does result in larger magnification -- however, the individually higher optical power element in this telescope is actually the eye lens. To achieve large … fisheye lens photo examples
The lens power equation - Lenses - Edexcel - BBC Bitesize
WebThe lens power equation If a lens has a shorter focal length it is said to be more powerful. The power of a lens is defined as the reciprocal of the focal length. WebFirst convert focal length into metres: f = 25 cm = 0.25 m \ [lens \\ power = \frac {1} {0.25} = 4.0 \\ D\] \ [lens \\ power = 4.0 \\ dioptres\] Example 2 A lens has a power of -3.33... WebA person needs a lens of power -5.5 diopters for correcting his distant vision. For correcting his near vision he needs a lens of power +1.5 diopters. What is the focal length of the lens required for correcting (i) distant vision (ii) near vision? Medium Solution Verified by Toppr (i) Correcting distant vision f= P1=1/(−5.5)=−0.18 m fisheye lens photo dog